The present invention relates to overload protection devices and assemblies that are used in restraint-camming apparatus for driving associated operating members in reciprocating movement, and more particularly, to an overload protection device for use in a restraint camming apparatus that operates operating members, such as terminal stitching heads that are commonly used in to insert conductive terminals in electrical connector housings.
Anti-overloading devices are used in restraint-camming apparatus for translating operating members in order to prevent apparatus, such as terminal insertion devices from exerting too much pressure or insertion force on a terminal. In terminal insertion devices where conductive terminals are inserted, or xe2x80x9cstitchedxe2x80x9d into corresponding openings arranged in insulative connector housings, the stitching head is operated in a reciprocating motion in two different directions, typically by a camming assembly. Sometimes, the openings in the conductor housing may be made misaligned and the terminals, when stitched, will impinge upon the connector housing rather than enter into the terminal openings.
When this occurs, it is desirable to have some measure of control and protection that prevents the stitching head from continuing its insertion movement when a strong resistance force exceeding a certain magnitude is encountered. This protection preferably prevents the stitching head from continuing in its insertion movement when a force greater than a preselected insertion force is encountered. If the stitching head continues in its movement against a preselected resistance force, the stitching head may break. Thus the need for this type of protection exists.
FIG. 8 of this application illustrates a known overload protection assembly used with a restraint camming apparatus. It can be seen that the conventional apparatus includes a first operating member 53 that is guided by a main linear guide 52 for reciprocating movement in two opposing directions. A secondary linear guide 51 is located between the first operating member 53 and a second operating member 54 such that the second operating member 54 is guided by the linear sub-guide 51. A restraint cam 55 of the apparatus that drives the first operating member 53 in its reciprocating movement is bounded by two cam followers 56 that are rotatably mounted to the first operating member 53. The second operating member 54 is able to resist a given load exerted thereon in the direction of the arrow in FIG. 8 by way of an associated compression spring 57. Rotation of the restraint cam 55 about its axle 58 causes the first operating member 53 to move back and forth in reciprocating movement along the main linear guide 52, and carrying the second operating member 54.
Another known anti-overloading protection device is illustrated in FIG. 9, wherein a first operating member 63 is guided by an associated main linear guide 62. A sub-linear guide 61 is disposed between the first operating member 63 and a second operating member 64 so that the second operating member 64 may be guided by the sub-linear guide 61. A restraint cam 65 is bounded by two cam followers 66 rotatably mounted to the first and second operating members 63, 64. The second operating member 64 is pushed against the first operating member 63 by a compression spring 67 that exerts a force on the second operating member 64 and two associated blocks 68. Rotation of the restraint cam 65 about its axle 69 will cause the first operating member 63 to move back and forth along the main linear guide.
Use of either of the aforementioned sub-linear guides 51, 61 to apply a force on their respective first operating numbers 53, 63 increases the both size and weight of the anti-overloading devices, thus reducing the quickness with which the anti-overloading device can respond to a given action at increased speed. The known anti-overloading device of FIG. 8 is so constructed that it may be subjected directly to the load, preventing the device from being released from the overload. Therefore, increasing the strength of the opposing compression spring 57 will cause an adverse effect on the protecting capability provided by the device.
As for the apparatus illustrated in FIG. 9, a counter-moment, such as that shown by the arrow 70 will apparently cause one or the other cam follower 66 to abut the cam 65 in an unstable manner, thereby upsetting its equilibrium. Alternatively, a shear pin may be used to make the device resistant to an increased load amount, but the use of such a shear pin does not provide the capability to restore the apparatus and has a poor reproduction. Accordingly, it cannot have a good reliability in setting a required amount of permissible load.
One object of the present invention is therefore to provide an improved anti-overloading device for use in a restraint-camming apparatus for translating an associated operating member, which anti-overloading device is small enough in size so that it permits the device to be set for an increased amount of permissible load.
Another object of the present invention is to provide an anti-overloading device for use in a restraint camming apparatus that drives an operating member, such as a conductive terminal insertion head, in a reciprocating motion in two different and opposing directions, the overload protection device including a collapsible toggle assembly in the form of a cam follower interposed between the restraint cam and its associated operating member, the cam follower being movable between first and second operative positions, where in the first operative position, the cam follower is urged into contact with the restraint cam and transmits drive to the operating member and where in the second operative position, the cam follower collapses upon itself and moves out of contact with the restraint cam, thereby ending the transmission of drive to the operating member.
To attain this and other objects, an anti-overloading device according to the present invention uses a collapsible toggle assembly having a cam follower rotatably mounted for engaging the restraint cam and serving as a means for selectively transmitting drive from the restraint cam to its associated operating member.
Specifically, an anti-overloading device constructed in accordance with the principles of the present invention suitable for use in a restraint-camming apparatus having both a linear guide for guiding an associated operating member in a reciprocating movement and a restraint cam for moving the operating member in the reciprocating movement, is improved in that it includes a collapsible toggle assembly for mounting to the operating member, the toggle assembly having a xe2x80x9cUxe2x80x9d-shaped elongated body with two free arms, two linkages rotatably connected to the free ends of the opposite arms and on opposite sides thereon, a pin threading together the two linkages and rotatably supporting a cam follower that is engaged with the restraint cam, thereby putting the restraint cam in a controlled restraint condition between the cam follower and a second, guiding cam follower that is fixed to the operating member.
An anti-overloading device according to the present invention uses no sub-linear guides, and accordingly the size and weight of the device can be beneficially reduced. The toggle used in the anti-overloading device permits the associated parts of the device to move a relatively short distance for an increased amount of load.
Other objects and advantages of the present invention will be understood from the following description of anti-overloading devices according to preferred embodiments of the present invention, which are shown in accompanying drawings.